A Probabilistic Bundle Relay Strategy in Two-Hop Vehicular Delay Tolerant Networks

A persisting major challenge in Vehicular Delay- Tolerant Networks (VDTNs) is the delay minimization of data delivery when communicating nodes are stationary, arbitrarily deployed along roadsides and considerably apart that they cannot establish direct communication between each other. A source opportunistically releases bundles of data to cooperating vehicles passing by, hoping that they will successfully deliver them to the intended destination. Several complex strategies that tackle this problem have been proposed in the open literature. Nevertheless, these strategies often implicitly assume complete network knowledge. In this paper, we propose a rather simple Probabilistic Bundle Relay Strategy (PBRS) that relaxes the availability of complete network information. A queuing model is formulated to represent VDTN stationary sources where PBRS is deployed. We introduce the bundle release probability parameter which expresses the likelihood that a bundle is released by the source to a vehicle passing by. The proposed model is studied analytically and theoretical expressions of its characteristic parameters are all derived. In particular, we compute the time it takes to release a head-of-line bundle (referred to as the bundle´s service time). Moreover, the model is validated through a simulation study that gauges its merit. The simulation results show that even with partial network knowledge the proposed queueing model can guarantee acceptable bundle delivery delay.